It's really not that hard. See this handy rules explainer.
Balk Rules
You can't just be up there and just doin' a balk like that.
1a. A balk is when you
1b. Okay well listen. A balk is when you balk the
1c. Let me start over
1c-a. The pitcher is not allowed to do a motion to the, uh, batter, that prohibits the batter from doing, you know, just trying to hit the ball. You can't do that.
1c-b. Once the pitcher is in the stretch, he can't be over here and say to the runner, like, "I'm gonna get ya! I'm gonna tag you out! You better watch your butt!" and then just be like he didn't even do that.
1c-b(1). Like, if you're about to pitch and then don't pitch, you have to still pitch. You cannot not pitch. Does that make any sense?
1c-b(2). You gotta be, throwing motion of the ball, and then, until you just throw it.
1c-b(2)-a. Okay, well, you can have the ball up here, like this, but then there's the balk you gotta think about.
1c-b(2)-b. Fairuza Balk hasn't been in any movies in forever. I hope she wasn't typecast as that racist lady in American History X.
1c-b(2)-b(i). Oh wait, she was in The Waterboy too! That would be even worse.
1c-b(2)-b(ii). "get in mah bellah" -- Adam Water, "The Waterboy." Haha, classic...
1c-b(3). Okay seriously though. A balk is when the pitcher makes a movement that, as determined by, when you do a move involving the baseball and field of
2) Do not do a balk please.